For nearly 11 years, Michelle Knight endured unthinkable abuse as a captive in a Cleveland home. But today, her bright outlook has not been extinguished.

Ariel Castro kidnapped Knight in August of 2002 when she was just 21 years old. She was held along with two other young women until they were rescued on May 6 of last year. Knight's new book, "Finding Me," details her ordeal and how she has moved forward. She spoke with Savannah Guthrie that was previewed on TODAY Friday. The sit-down will air in its entirety as part of a larger Dateline NBC special on Sunday at 8 p.m. ET. Knight will appear live on TODAY on Monday.

"Sometimes in life, you have a dark past that makes you who you are, but it doesn't define who you are,'' Knight told Guthrie.

Knight is now focused on making the most of her life. She lives in her own apartment now and is taking cooking classes in hopes of becoming a chef. She has even changed her name.

"I felt like every brand new start needs new beginnings,'' she said. "My name is Lillian Rose Lee."

That resilience helped keep Knight, who now goes by Lilly, alive during her captivity, when her relentless abuse made her consider suicide. Knight's deep bond with Gina DeJesus, who was kidnapped by Castro in 2004 when she was 14 years old, helped Knight survive.

"There were days like he'll come in and he'll just do bad things in front of me, and I'll take her hand and I'll tell her everything's gonna be OK,'' Knight said. "One day we'll get out. One day we'll be free. One day we won't be voiceless."

Castro was sentenced to life in prison plus 1,000 years after pleading guilty to 937 counts of rape, kidnapping and aggravated murder, and he committed suicide one month into his sentence.

When her ordeal was at her worst, Knight was still able to write lines in her diary like, "Vibrant butterfly, full of life, every time I see one it reminds me how precious life can truly be." Now she feels like she has become the butterfly, ready to spread her wings.

"(A butterfly) that's able to express herself the way she wants now, and able to be free without control and no worries,'' she said. "I'm that butterfly. Freedom to fly."